THE CODLING MOTH IN MICHIGAN. 83 



The laboratory observations at Douglas, Mich., show that the num- 

 ber of molts of the codling moth may vary even under uniform con- 

 ditions. The great majority, however, have six larval instars, a few 

 only five, and very exceptionally seven instars. 



Head measurements, when used in a series of consecutive tests, 

 will bring out the number of molts of the larvae, but this method can 

 not be relied upon in determining the instars of any given larva, 

 owing to the variability in size. The final averages as shown in 

 Table LXXXI bring out the average widths of the head of the cod- 

 ling moth larva in its successive instars and also the rate of increase 

 of each molt. 



In 1881 Edwards J pointed out that the number of molts depends 

 largely upon climatic conditions, these molts being more frequent in 

 warm climates where the growth is rapid than in cold climates where 

 the growth is retarded. The present records on the number of molts 

 of the codling moth in Michigan and in the Ozarks corroborate 

 Edwards's statement. Jenne found seven instars in the South, while 

 in the North the writer found six instars. 



CANNIBALISM AMONG LARVAE OF THE CODLING MOTH. 



In confinement, when a large number of mature codling moth larvae 

 are kept together, it sometimes happens that certain larvae will 

 attack and kill weaker ones and later devour them. After such a 

 feast the cannibal larva assumes a dull, turbid color and can be readily 

 recognized from the. rest. It is evident that cannibalism among the 

 larvae also takes place under normal conditions. It has frequently 

 been noted that a number of newly hatched larvae have entered the 

 same apple, but only a single or a few larvae matured in the same 

 fruit. Occasionally larvae have been collected from bands which had 

 the characteristic appearance of cannibal larvae. 



CODLING MOTH LARV.E REMAINING TWO SEASONS IN THE LARVAL 



STAGE. 



An unusual observation on the duration of the larval stage of the 

 codling moth was made in 1909 and 1910 by Mr. R. W. Braucher at 

 Douglas, Mich. In the fall of 1908 a number of larvae were collected 

 for rearing purposes and for studies to be made the following spring. 

 Two of the larvae failed to transform in 1909 and both were alive the 

 following spring, 1910. On April 30 one larva had pupated; the 

 other larva died June 24. The pupa, too, finally failed and was found 

 dead July 18. Considering that the larva left the fruit about Sep- 

 tember 1, 1908, or possibly much earlier, we find that one of the insects 



i Psyche, vol. 3, p. 159, 



